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MENTAL PROTECTION AGENCY »
U.S. ENVIRONMENTAL PROTECTION AGENCY
Hybrid Powertrain Technology
A Glance at Clean Freight Strategies
ENERGY &
FUEL SAVINGS
Long Haul Hybrid
Gallons Saved:
1,333 gallons
CO2 Savings:
13.5 metric tons
Fuel Economy
Increase:
9%
MPG
(original 6 mpg):
6.52 mpg
Reduction in Fuel
Consumption:
8%
Fuel Cost Savings:
$5,066
Hybrid vehicles that use two or more distinct power sources to operate can
provide fuel savings in both long-haul combination trucks and stop-and-qo freight
applications as well as cut greenhouse gas emissions. The amount of savings is
highly dependent on the drive cycle.
What is the challenge?
When a truck decelerates or brakes, the kinetic energy of the moving vehicle is typically lost. This
energy loss is particularly large for trucks operating in urban areas, where vehicles make frequent
starts and stops. If the kinetic energy of a braking truck can be captured and harnessed, the truck
can achieve better fuel economy and lower emissions.
What is the solution?
Hybrid powertrain technology is a method to capture this energy and improve fuel economy.
Hybrid technology uses two power sources to move the vehicle, a main source and a secondary
source. The secondary power source provides an extra boost to the main power source (usually
an internal combustion engine) when the vehicle needs extra power, such as when climbing a hill
or accelerating to pass. This usually makes it possible to use a main power source that operates
more efficiently and could be downsized. When the main engine is downsized, other powertrain
components, such as the radiator, can be downsized as well.
One of the primary benefits of hybrid powertrain technology is the ability to reclaim a portion
of the energy otherwise lost to braking or deceleration. A variety of options exist to capture and
store this kinetic energy for later use. One option relies on the kinetic energy of the vehicle to
generate electricity, which can be stored in a battery. Another option is to store the electricity in
ultracapacitors, which charge quickly but are costly. A third option stores energy as hydraulic
pressure. Hydraulic fluid inside a sealed cylinder pushes against a "bladder" of inert nitrogen
gas, which is compressed and thus stores energy. Flywheels have also been used to store the
extra energy.
While the first commercial applications of hybrid powertrain technology have been passenger
vehicles, it is actually more efficient to place hybrid technology in heavier vehicles like trucks.
Since a vehicle with greater mass requires more power to stop, more potential energy can be
recaptured during braking or deceleration. Larger vehicles also tend to have more available
space for packaging the hybrid power train components. Heavy-duty trucks typically cost more
than passenger vehicles, so the additional cost for the technology can be a smaller
percentage of total vehicle cost.
Savings and benefits
In pick-up and delivery service, it is estimated that truck fuel consumption
can be reduced from 25 to 50 percent using hybrid powertrain technology.
Fuel savings depend on the type of hybrid technology, the amount of
regenerative braking energy, and the amount of engine efficiency improve-
ments. Atypical long-haul combination truck could save about $5,000 in
fuel costs and reduce greenhouse gas emissions by over 13 metric tons
per year. Benefits for a typical stop-and-go truck include fuel savings of
about $1,000 and 4 metric tons of greenhouse gases each year. At least
three major parcel delivery companies are exploring the use of hybrid
technology for step vans. Preliminary results from some parcel
delivery companies indicate hybrid trucks expect about a 40
percent improvement in fuel economy.
Continued
U.S. EPA SmartWay | EPA-420-F-16-032 | June 2016 | www.epa.gov/smartway
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SmartWay
MENTAL PROTECTION AGENCY »
U.S. ENVIRONMENTAL PROTECTION AGENCY
Hybrid Powertrain Technology
A Glance at Clean Freight Strategies continued
ENERGY &
FUEL SAVINGS
Stop & Go
Gallons Saved:
394 gallons
CO2 Savings:
4 metric tons
Fuel Economy
Increase:
33%
MPG
(original 6 mpg):
11.39 mpg
Reduction in Fuel
Consumption:
25%
Fuel Cost Savings:
$1,497
NIEX] STEPS
IUse hybrid power
train technology
in a fleet setting.
2Set up an evalu-
ation process to
assess hybrid power
train technology with
different fleet drive
cycles.
S
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